This application is directed to the production of high quality hydrocarbon fractions by hydrocracking high boiling hydrocarbons.
One of the most valuable products of the refining of crude mineral oils is lubricating oil. Common practice is to recover lubricating oil components by extracting undesirable components, such as sulfur compounds, oxygenated compounds, and aromatics, from a straight run distillate fraction with a selective solvent. However, with the gradual decline in the availability of paraffinic base crudes and a corresponding increase in the proportion of naphthenic and mixed naphthenic and asphaltic base crudes, it is becoming increasingly difficult to recover sufficient quantities of components suitable for lubricating oils by extraction.
One method which has been suggested as a remedy of this situation is hydrogenation of high boiling hydrocarbon charge stocks which do not contain a substantial quantity of lube oil components in order to produce such components. An example of this method is represented in U.S. Pat. No. 3,142,635, incorporated herein by reference, teaching the production of very high viscosity index oils in high yields of a unique kind of using a special catalyst. This method teaches the use of hydrocracking catalysts such as platinum on silica-alumina as well as others taught in U.S. Pat. No. 2,945,806, incorporated herein by reference. The use of such catalysts results in a product of high viscosity index. However, it is recognized that substantial amounts of undesirable low viscosity index polycyclic aromatics which are oxidatively unstable will remain in the lube oil produced by hydrocracking unless removed by distillation. Another way of dealing with such impurities is taught in U.S. Pat. No. 3,530,061, incorporated herein by reference, which employs hydroprocessing the hydrocracked product with a hydrogenation-dehydrogenation catalyst comprising a support material of low cracking activity, e.g., platinum on alumina at temperatures and pressures which limit conversion to 600.degree. F..sup.- products. However, this procedure suffers from the drawback of requiring an additional hydroprocessing step. In U.S. Pat. No. 4,176,090, catalysts which comprise layered clays (smectites) intercalated with inorganic metal polymers, e.g., aluminum chlorhydrol, which form polymeric cationic hydroxy metal complexes are disclosed as suitable for conventional petroleum conversion processes such as catalytic cracking, hydrocracking, hydrotreating, and isomerization. U.S. Pat. No. 4,579,832 discloses the use of layered smectite clays, e.g., montmorillonite, which are cross-linked with hydroxy-Al oligomers, as hydrocracking catalysts.